Electronic devices comprising digit line contacts and related systems and methods

ABSTRACT

A semiconductor device comprises laterally-neighboring word lines having respective word line caps thereon, an active region between the laterally-neighboring word lines and word line caps, an insulating material and a semiconductive material adjacent the word line caps, and a digit line contact between opposing substantially vertical surfaces of the semiconductive material, between opposing substantially vertical surfaces of the insulating material, adjacent to substantially horizontal surfaces of the word line caps, and between opposing substantially vertical surfaces of the word line caps. A transition surface extending between and connecting the substantially horizontal surface and the substantially vertical surface of the respective word line caps projects toward a longitudinal axis extending centrally through the digit line contact. Methods of forming the semiconductor device are also disclosed, as are electronic systems including the semiconductor device.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.16/258,296, filed Jan. 25, 2019, the disclosure of which is herebyincorporated in its entirety herein by this reference.

TECHNICAL FIELD

Embodiments of the disclosure relate to the field of semiconductordevice design and fabrication. More specifically, embodiments disclosedherein relate to semiconductor devices including substantially unetchedword line caps having substantially vertical and substantiallyhorizontal surfaces defining at least a portion of a perimeter of adigit line contact, and to related electronic systems and methods.

BACKGROUND

Semiconductor device designers often desire to increase the level ofintegration or density of features within a. semiconductor device byreducing the dimensions of the individual features and by reducing theseparation distance between neighboring features. In addition,semiconductor device designers often desire to design architectures thatare not only compact, but offer performance advantages, as well assimplified designs.

A relatively common semiconductor device is a memory device. A memorydevice may include a memory array having a number of memory cellsarranged in a grid pattern. One type of a memory cell is a dynamicrandom access memory (DRAM) cell. In the simplest design configuration,a DRAM cell includes one access device, such as a transistor, and onestorage device, such as a capacitor. Modern applications for memorydevices can utilize vast numbers of DRAM cells, arranged in an array ofrows and columns. The DRAM cells are electrically accessible throughdigit lines and word lines arranged along the rows and columns of thearray.

FIG. 1 illustrates a transistor 10 of a conventional DRAM cell. Thetransistor 10 includes an active area 12 extending between neighboringword lines 14 and shallow trench isolation (ST1) regions 16 extendingbetween neighboring active areas 12 to isolate the active areas 12 fromone another. An oxide region 18 is provided about the word lines 14between the word lines 14 and the active area 12 and the STI region 16,respectively. Each word line 14 is provided with a word line cap 20. Adigit line contact 22 (e.g., digit line plug) is formed on the activearea 12 in a digit line contact opening 30 (FIG. 11) defined by surfaces25 of a conductive region 26, an oxide region 27, andlaterally-neighboring word line caps 20. A digit line 24 is electricallyconnected to the digit line contact 22. The digit line 24 includes apolysilicon region 21 and another conductive region 23 formed adjacent(e.g., longitudinally adjacent, on, over) to the oxide region 27 andanother polysilicon region (e.g., the conductive region 26) that eachneighbor the digit line contact 22, A digit line cap 28 is formedadjacent to the digit line 24,

As illustrated in FIG. 1 and in FIG. 11, which is discussed in furtherdetail below, the word line caps 20 are etched during formation of theof the transistor 10 such that at least a portion of the word line caps20 are removed. Accordingly, the respective word line caps 20 may have arecess formed therein and defined by a sloped surface 13 and asubstantially horizontal surface 15. The word line caps 20 are etchedsuch that the sloped surface 13 extends to and intersects with thesubstantially horizontal surface 15 at a transition surface 17 (e.g.,corner) that projects into the word line cap 20 and away from alongitudinal axis 31. Accordingly, the opening 30 in which the digitline contact 22 is formed is substantially U-shaped.

A continuing goal of the semiconductor industry has been to increase thememory density (e.g., the number of memory cells per memory die) ofmemory devices. While a footprint of the memory devices of memory cells,including transistors, continues to be scaled down to increase thememory density, decreasing the size of one or more components of memorycells may negatively affect performance and places ever increasingdemands on the methods used to form the memory device features. Forexample, one of the limiting factors in the continued shrinking ofmemory devices is the resistance of the contacts associated therewith.For example, in a DRAM device exhibiting a dual bit memory cellstructure, the digit line contact 22 is provided between the digit line24 and an access device (e.g., a transistor) formed in or above asubstrate, and storage node contacts are formed between the accessdevice and a storage node (e.g., a capacitor) where electrical chargemay be stored. As the dimensions of memory device (e.g., DRAM device)features decrease, the distance between neighboring digit line contactsof the memory arrays decreases, increasing coupling capacitances betweenthe adjacent (e.g., laterally-neighboring) digit line contacts. Withgreater amounts of coupling capacitances between the adjacent digit linecontacts, current and voltage pulses used to select memory cells can,undesirably, be distributed to neighboring memory cells in a memoryarray and thus reduce the reliability of the neighboring memory cellsand the memory array as a whole.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a conventionalsemiconductor device;

FIGS. 2 through 10 are schematic cross-sectional views illustrating amethod of forming a semiconductor device, in accordance with embodimentsof the disclosure;

FIGS. 11 and 12 are cross-sectional micrographs of a conventionalsemiconductor device and the semiconductor device according toembodiments of the disclosure, respectively; and

FIG. 13 is a schematic block diagram illustrating an electronic system,in accordance with embodiments of the disclosure.

DETAILED DESCRIPTION

The illustrations included herewith are not meant to be actual views ofany particular systems or semiconductor devices, but are merelyidealized representations that are employed to describe embodimentsherein. Elements and features common between figures may retain the samenumerical designation except that, for ease of following thedescription, for the most part, reference numerals begin with the numberof the drawing on which the elements are introduced or most fullydescribed.

The following description provides specific details, such as materialtypes, material thicknesses, and processing conditions in order toprovide a thorough description of embodiments described herein. However,a person of ordinary skill in the art will understand that theembodiments disclosed herein may be practiced without employing thesespecific details. Indeed, the embodiments may be practiced inconjunction with conventional fabrication techniques employed in thesemiconductor industry. In addition, the description provided hereindoes not form a complete description of a semiconductor device or acomplete description of a process flow for fabricating a semiconductordevice. The structures described below do not form completesemiconductor devices, or systems for processing semiconductor devices.Only those process acts and structures necessary to understand theembodiments described herein are described in detail below. Additionalacts to form a complete semiconductor device or a system for processinga semiconductor device may be performed by conventional techniques.

As used herein, the term “substantially” in reference to a givenparameter, property, or condition means and includes to a degree thatone of ordinary skill in the art would understand that the givenparameter, property, or condition is met with a degree of variance, suchas within acceptable manufacturing tolerances. By way of example,depending on the particular parameter, property, or condition that issubstantially met, the parameter, property, or condition may be at least90.0% met, at least 95.0% met, at least 99.0% met, even at least 99.9%met, or even 100.0% met.

As used herein, the term “about” or “approximately” in reference to anumerical value for a particular parameter is inclusive of the numericalvalue and a degree of variance from the numerical value that one ofordinary skill in the art would understand is within acceptabletolerances for the particular parameter. For example, “about” or“approximately” in reference to a numerical value may include additionalnumerical values within a range of from 90.0 percent to 110.0 percent ofthe numerical value, such as within a range of from 95.0 percent to105.0 percent of the numerical value, within a range of from 97.5percent to 102.5 percent of the numerical value, within a range of from99.0 percent to 101.0 percent of the numerical value, within a range offrom 99.5 percent to 100.5 percent of the numerical value, or within arange of from 99.9 percent to 100.1 percent of the numerical value.

As used herein, any relational term, such as “first,” “second,” “over,”“above,” “below,” “up,” “down,” “upward,” “downward,” “top,” “bottom,”“top-most,” “bottom-most,” and the like, is used for clarity andconvenience in understanding the disclosure and accompanying drawingsand does not connote or depend on any specific preference, orientation,or order, except where the context clearly indicates otherwise.

As used herein, the term “configured” refers to a size, shape, materialcomposition, orientation, and arrangement of one or more of at least onestructure and at least one apparatus facilitating operation of one ormore of the structure and the apparatus in a pre-determined way.

As used herein, a “contact” refers to a connection facilitating aconductive pathway between at least two features.

As used herein, the terms “longitudinal,” “vertical,” “lateral,” and“horizontal” are in reference to a major plane of a substrate (e.g.,base material, base structure, base construction, etc.) in or on whichone or more structures and/or features are formed and are notnecessarily defined by earth's gravitational field. A “lateral” or“horizontal” direction is a direction that is substantially parallel tothe major plane of the substrate, while a “longitudinal” or “vertical”direction is a direction that is substantially perpendicular to themajor plane of the substrate. The major plane of the substrate isdefined by a surface of the substrate having a relatively large areacompared to other surfaces of the substrate.

As used herein, “vertically-neighboring” or “longitudinally-neighboring”features (e.g., structures, devices) means and includes features locatedvertically proximate to one another. The features may directly contactone another or may be separated from one another by one or moreadditional features. In addition, as used herein,“horizontally-neighboring” or “laterally-neighboring” features (e.g.,structures, devices) means and includes features located horizontallyproximate to one another.

The methods and structures of the disclosure may facilitate increasedfeature density, providing enhanced performance in semiconductor devicesstructures (e.g., DRAM device structures, such as DRAM cells) andsemiconductor devices (e.g., DRAM devices) that rely on high featuredensity by decreasing digit line capacitance.

FIGS. 2 through 9 illustrate various stages of a fabrication process toform a semiconductor device 100 shown in FIGS. 9 and 10, according toembodiments of the disclosure. Referring to FIG. 2, a structure 102 maybe formed on a substrate (not shown) to include an active region 104(e.g., digit line contact region) extending betweenlaterally-neighboring word lines 106 and between STI regions 108 thatseparate and isolate laterally-neighboring active regions 104. The wordlines 106 may be formed in a word line trench 110 having a gatedielectric material 112 disposed on substantially vertical surfacesthereof. Each word line 106 may have a respective word line cap 114formed adjacent an upper, substantially horizontal surface thereofwithin the word line trench 110. The structure 102 further includes astack 103 of at least one stack material. The stack material maycomprise at least one insulating material and at least onesemiconductive material. The stack 103 may be formed adjacent torespective upper, horizontal surfaces of the STI regions 108, the wordline caps 114, and the active region 104. In some embodiments, the stack103 comprises a first insulating material 116 (e.g., electricallyinsulating material, dielectric), a semiconductive material 118 adjacent(e.g., longitudinally-neighboring, on, over) the first insulatingmaterial 116, and a second insulating material 120 adjacent thesemiconductive material 118. A first hard mask material 122 may beformed adjacent the second insulating material 120, and a second hardmask material 124 may be formed adjacent the first hard mask material122.

The active region 104 may be formed of and include a semiconductivematerial. The semiconductive material may include, but not limited to,at least one of a silicon material, a silicon-germanium material, agermanium material, a gallium arsenide material, a gallium nitridematerial, an indium phosphide material, or a combination thereof. Insome embodiments, the active region 104 is formed of and includes asilicon material, or a material that includes elemental silicon or acompound of silicon. In such embodiments, the active region 104comprises a monocrystalline silicon.

The STI region 108 may be formed of and include an insulating material.The insulating material of the STI region 108 may include, but is notlimited to, an oxide material (e.g., silicon dioxide, phosphosilicateglass, borosilicate glass, borophosphosilicate glass, fluorosilicateglass, aluminum oxide, a combination thereof), a nitride material (e.g.,silicon nitride), an oxynitride material (e.g., silicon oxynitride),amorphous carbon, or a combination thereof. In some embodiments, the STIregion 108 is a silicon oxide (e.g., silicon dioxide).

The word lines 106 may each be formed of and include a conductivematerial. The conductive material of the word lines 106 may include, butis not limited to, a metal (e.g., tungsten, titanium, nickel, platinum,gold), a metal alloy, a metal-containing material (e.g., metal nitrides,metal silicides, metal carbides, metal oxides), a conductively-dopedsemiconductor material (e.g., conductively-doped silicon,conductively-doped germanium, conductively-doped silicon germanium,etc.), or combinations thereof. By way of non-limiting example, each ofthe word lines 106 may comprise at least one of titanium nitride (TiN),tantalum nitride (TaN), tungsten nitride (WN), titanium aluminum nitride(TiAlN), elemental titanium (Ti), elemental platinum (Pt), elementalrhodium (Rh), elemental iridium (Ir), iridium oxide (IrOx), elementalruthenium (Ru), ruthenium oxide (RuOx), alloys thereof, or combinationsthereof.

The gate dielectric material 112 may be formed of and include adielectric oxide material (e.g., silicon dioxide; phosphosilicate glass;borosilicate glass; borophosphosilicate glass; fluorosilicate glass;aluminum oxide; high-k oxides, such as hafnium oxide (HfO_(x)); acombination thereof), a dielectric nitride material (e.g., siliconnitride (SiN)), a dielectric oxynitride material (e.g., siliconoxynitride (SiON)), a dielectric carbonitride material (e.g., siliconcarbonitride (SiCN)), and a dielectric carboxynitride material (e.g.,silicon carboxynitride (SiOCN)), and amorphous carbon. In someembodiments, the gate dielectric material 112 comprises silicon dioxide(SiO₂).

The word line caps 114 may be formed of and include an insulatingmaterial. In some embodiments, the word line caps 114 comprise siliconnitride (e.g., Si3N4). The first insulating material 116 and the secondinsulating material 120 may be formed of and include a silicon dioxide(SiO₂). In some embodiments, the semiconductive material 118 is anundoped polysilicon material. In such embodiments, the semiconductivematerial 118 comprises a polysilicon material substantially free ofimpurities and may be configured to serve as an insulating material. Thefirst hard mask material 122 may be formed of and include an amorphouscarbon material. The second hard mask material 124 may comprise adielectric anti-reflective coating (DARC).

The structure 102 including the active region 104, word lines 106, STIregions 108, gate dielectric material 112, word line caps 114, the firstinsulating material 116, the semiconductive material 118, the secondinsulating material 120, the first hard mask material 122, and thesecond hard mask material 124 may be previously formed by conventionaltechniques using one or more formation acts including, but not limitedto, in situ growth processes, physical vapor deposition, chemical vapordeposition, atomic layer deposition, or a combination thereof, and oneor more patterning (e.g., material removal) steps including, but notlimited to, masking, etching, planarizing, or a combination thereof

With continued reference to FIG. 2, the second hard mask material 124may have at least one opening 123 previously patterned therein to forman opening 125 (FIG. 3) through the first hard mask material 122 and thesecond insulating material 120. The opening 125 may be formed bysubjecting the first hard mask material 122 and the second insulatingmaterial 120 to a material removal process such as at least one etchingprocess (e.g., at least one dry etching process, such as at least one ofa reactive ion etching (ME) process, a deep ME process, a plasma etchingprocess, a reactive ion beam etching process, and a chemically assistedion beam etching process; at least one wet etching process, such as atleast one of a wet chemical etching process, a buffered hydrofluoricacid etching process, and a buffered oxide etching process). In someembodiments, the opening 125 is formed by a dry etching processemploying an O₂—SO₂ plasma gas to selectively remove the first hard maskmaterial 122 and the second insulating material 120. In suchembodiments, the semiconductive material 118 may serve as an etch stopmaterial during the etching process to form the opening 125.

After the opening 125 is formed, the second hard mask material 124 maybe removed, as illustrated in FIG. 3. With reference to FIG. 4, theopening 125 may be extended to form an opening 126 through thesemiconductive material 118, through the first insulating material 116,and at least partially into the active region 104 to expose an upper,horizontal surface 117 of the active region 104. The opening 126 may beformed by selectively removing a portion of the semiconductive material118, the first insulating material 116, and the active region 104extending between laterally-neighboring word line caps 114. The opening126 may be formed by subjecting at least a portion of the semiconductivematerial 118, the first insulating material 116, and the active region104 extending between laterally-neighboring word line caps 114 to atleast one material removal process. The material removal processincludes exposing (e.g., removing material adjacent to) substantiallyvertical surfaces of the first hard mask material 122, substantiallyvertical surfaces of the semiconductive material 118, substantiallyvertical surfaces of the first insulating material 116, substantiallyhorizontal surfaces 113 of the respective word line caps 114,substantially vertical surfaces of the word line caps 114, and thesubstantially horizontal surface 117 of the active region 104.

The material removal process may be a selective etching (e.g., selectiveremoval) process. In some embodiments, the etching process may be ananisotropic dry etching by which a bias voltage is applied to generate aplasma gas by high-frequency excitation to cause ions in the plasma gasonto the surface of the semiconductive material 118, the firstinsulating material 116, the active region 104, and the word line caps114 to selectively remove (e.g., etch) portions of the foregoing. Insome embodiments, the semiconductive material 118, the first insulatingmaterial 116, and the active region 104 may be exposed to achlorine-containing plasma gas such as a boron trichloride (BCl₃) plasmagas. The composition of the plasma gas, the frequency of the plasma gasexcitation (e.g., power bias), etc. may be tailored such that thesemiconductive material 118, the first insulating material 116, and theactive region 104 are substantially removed without substantiallyremoving (e.g., etching) or only slightly removing the word line caps114. In some embodiments, the plasma gas composition (e.g., etchant) isselected such that the semiconductive material 118, the first insulatingmaterial 116, and the active region 104 are removed (e.g., etched) at agreater rate (e.g., etch rate) than the word line caps 114. Moreparticularly, the plasma gas composition is selected such that thesemiconductive material 118, the first insulating material 116, and theactive region 104 are removed at a rate that is between about five timesand about ten times greater than the rate at which the word line caps114 are removed.

Accordingly, the semiconductive material 118, the first insulatingmaterial 116, and the active region 104 may be substantially removedwithout substantially removing the word line caps 114, as illustrated inFIG. 4. As the word line caps 114 are not substantially removed, thesubstantially horizontal surface 113 and the substantially verticalsurface 115 of the respective word line caps 114 remains. Further, asthe word line caps 114 are maintained (e.g., not substantially removed),a transition surface 121 (e.g., corner, intersection) extending betweenand connecting the substantially horizontal surface 113 and thesubstantially vertical surface 115 of the respective word line caps 114projects (e.g., points, extends) toward a longitudinal axis 144 of theopening 126. The transition surface 121 may define a substantially sharpor pointed edge as illustrated in the schematic of FIG. 4. In otherembodiments, the word line caps 114 may be partially etched such thatthe transition surface 121 of the respective word line caps 114 may berounded or form a curved surface as illustrated in FIG. 12 and as shownby dashed lines in FIG. 6.

By way of example only, if the active region 104 is formed ofmonocrystalline silicon, the word lines caps 114 are formed of siliconnitride, the first insulating material 116 is formed of an oxide, andthe semiconductive material 118 is formed of polysilicon, portions ofthe active region 104, the first insulating material 116, and thesemiconductive material 118 may be selectively removed withoutsubstantially removing a portion of the word lines caps 114.

Subsequently, as illustrated in FIG. 5, the first hard mask material 122may be removed in a material removal process to expose an upper,horizontal surface 119 of the second insulating material 120. With thefirst hard mask material 122 removed, an opening 130 remains extendingthrough the second insulating material 120, through the semiconductivematerial 118, through the first insulating material 116, and at leastpartially into the semiconductive material of the active region 104between the laterally-neighboring word line caps 114. The opening 130may be referred to as a digit line contact (e.g., digit line plug)opening.

Surfaces 142 collectively defining the opening 130 include the opposingsubstantially vertical surfaces of the semiconductive material 118, theopposing substantially vertical surfaces of the first insulatingmaterial 116, the substantially horizontal surfaces 113 of therespective word line caps 114, the opposing substantially verticalsurfaces 115 of the word line caps 114, a transition surface 121extending between and connecting the substantially horizontal surface113 and the substantially horizontal surface 117 of the word line caps114, and the substantially horizontal surface 117 of the active region104.

With continued reference to FIG. 5, the opening 130 may be subjected toat least one cleaning process. The cleaning process may remove siliconmaterial or other material that may have formed adjacent to an upper,horizontal surface 117 of the active region 104 during formation of theopening 126. More particularly, the cleaning process may remove siliconmaterial from the upper, horizontal surface 117 of the active region 104exposed in the opening 130. The cleaning process may be a light etchprocess or a descum process. In some embodiments, the upper, horizontalsurface 117 of the active region 104 is subjected to an ammonia (NH₃)forming gas or a mixture of oxygen and tetrafluoromethane (O₂—CF₄) gasto remove (e.g., etch) a portion of the silicon on or included in theactive region 104.

Optionally, a barrier material 140 may be formed within the opening 130,as illustrated in FIG. 5. The barrier material 140 may be formed (e.g.,deposited) along at least a portion of the vertical surfaces 142 of theopening 130. More particularly, the barrier material 140 may be formed(e.g., deposited) along a vertical surface of the semiconductivematerial 118. In some embodiments, the barrier material 140 may also beformed along a vertical surface of the first insulating material 116.The barrier material 140 may be selected to comprise a material thatinhibits diffusion of dopants in a conductive material 146 (FIG. 6) of adigit line contact (e.g., digit line plug) 150 (FIG. 8) into thesemiconductive material 118, which may be undoped polysilicon. Thebarrier material 140 may intervene between the substantially verticalsurfaces of the semiconductive material 118 and the first insulatingmaterial 116 within the opening 130 and the digit line contact 150. Insome embodiments, the barrier material 140 comprises a silicon nitridematerial and/or a silicon oxide material.

With reference to FIG. 6, a conductive material 146 may be formed (e.g.,deposited) within the opening 130 such that the opening 130 issubstantially filled with the conductive material 146. The conductivematerial 146 may also be formed to extend outside of the opening 130such that the conductive material 146 is formed adjacent the upper,horizontal surface 119 of the second insulating material 120. As theopening 130 is defined by surfaces 142, the conductive material 146disposed within the opening 130 may have a perimeter that issubstantially complementary in shape to a shape of the opening 130 asdefined by the surface 142. The conductive material 146 may be formedby, for example, atomic layer deposition (ALD), chemical vapordeposition (CVD), physical vapor deposition (PVD), low pressure chemicalvapor deposition (LPCVD), plasma-enhanced chemical vapor deposition(PECVD), another deposition method, or combinations thereof. In someembodiments, the conductive material 146 comprises doped polysilicon,such as a polysilicon material having impurities.

Accordingly, a method of forming the semiconductor device comprisesforming a semiconductive material extending betweenlaterally-neighboring word lines having respective word line capsthereon, an insulating material adjacent the word line caps, and anothersemiconductive material adjacent the insulating material. A portion ofthe another semiconductive material, the insulating material, and thesemiconductive material is selectively removed without substantiallyremoving the neighboring word line caps to form an opening through theanother semiconductive material, through the insulating material, andlaterally between the word line caps. A conductive material is formed inthe opening. In additional embodiments, a method of forming asemiconductor device comprises forming a semiconductive materialextending laterally between neighboring word lines having respectiveword line caps thereon, a first material adjacent the word line caps,and a second material adjacent the first material. An opening is formedthrough the second material, through the first material, and at leastpartially into the semiconductive material between the respective wordline caps. The opening is defined by opposing substantially verticalsurfaces of the second material, opposing substantially verticalsurfaces of the first material, substantially horizontal surfaces of theword line caps, opposing substantially vertical surfaces of the wordline caps, and transition surfaces extending between the substantiallyhorizontal surface and the substantially vertical surface of therespective word line caps. The transition surfaces project toward thelongitudinal axis extending centrally through opening. A conductivematerial is formed in the opening.

With reference to FIG. 7, the conductive material 146 may be subjectedto at least one material removal process to remove a portion of theconductive material 146 extending beyond the opening 130. Moreparticularly, the conductive material 146 extending adjacent to theupper, horizontal surface 119 of the second insulating material 120 andat least a portion of the conductive material 146 within the opening 130adjacent to the second insulating material 120 may be removed to form adigit line contact 150. The conductive material 146 may be subjected toan etching process (e.g., an anisotropic etching process) to remove aportion of the conductive material 146. In some embodiments, theconductive material 146 is removed such that an upper, horizontalsurface 148 of the digit line contact 150 is recessed relative to theupper, horizontal surface 119 (FIG. 8) of the second insulating material120. A lower surface 149 of the digit line contact 150 is in contact(e.g., physical contact, electrical contact) with the upper, horizontalsurface 117 of the active region 104. As shown in the cross-section ofFIG. 7, the digit line contact 150 exhibits a T-shape, with sidewalls ofa lower portion of the digit line contact 150 being substantiallyvertical and the transition surface 121 of the word line caps 114exhibiting the substantially sharp or pointed edges. In contrast,sidewalls of conventional word line caps 20 and conventional digit linecontact 22 are sloped.

With reference to FIG. 8, the second insulating material 120 may besubjected to at least one material removal process such that an upper,horizontal surface 152 of the semiconductive material 118 is exposed.The upper, horizontal surface 152 of the semiconductive material 118 maybe substantially coplanar (e.g., coextensive) with the upper, horizontalsurface 148 of the digit line contact 150. With reference to FIG. 9, abarrier material 156 may be optionally formed adjacent to the upper,horizontal surface 152 of the semiconductive material 118 and adjacentto the upper, horizontal surface 148 of the digit line contact 150. Thebarrier material 156 may comprise a metallic material such as titaniumnitride (TiN) or tungsten nitride (WN).

With reference to FIGS. 9 and 10, which are cross-sectional views of thesemiconductor device 100 taken perpendicular to each other, anotherconductive material may be formed (e.g., deposited) adjacent to (e.g.,on) the upper, horizontal surface 152 of the semiconductive material 118to form a digit line 154. In some embodiments, the digit line 154 may beformed on an upper, horizontal surface of the barrier material 156. Inother embodiments, the digit line 154 may directly contact and extendadjacent to and between laterally-neighboring digit line contacts 150extending in a direction (e.g., the y direction of FIG. 9) substantiallyperpendicular to the direction (e.g., the x direction into the page ofFIG. 10) of the word lines 106.

The digit line 154 may comprise a conductive material, such as, forexample, tungsten, titanium, nickel, platinum, rhodium, ruthenium,aluminum, copper, molybdenum, iridium, silver, gold, a metal alloy, ametal-containing material (e.g., metal nitrides, metal silicides, metalcarbides, metal oxides), a material including at least one of titaniumnitride (TiN), tantalum nitride (TaN), tungsten nitride (WN), titaniumaluminum nitride (TiAlN), iridium oxide (IrO_(x)), ruthenium oxide(RuO_(x)), alloys thereof, a conductively-doped semiconductor material(e.g., conductively-doped silicon, conductively-doped germanium,conductively-doped silicon germanium, etc.), polysilicon, othermaterials exhibiting electrical conductivity, or combinations thereof.

A digit line cap 158 may be formed adjacent the digit line 154. Thedigit line cap 158 may be formed of and include a dielectric material.In some embodiments, the digit line cap 158 comprises silicon nitride(SiN).

Accordingly, in some embodiments, the semiconductive device compriseslaterally-neighboring word lines having respective word line capsthereon, an active region extending between the laterally-neighboringword lines and word line caps, a stack material adjacent the word linecaps, and a digit line contact disposed between opposing substantiallyvertical surfaces of the stack material, adjacent to substantiallyhorizontal surfaces of the word line caps, and between opposingsubstantially vertical surfaces of the word line caps. A transitionsurface between and connecting the substantially horizontal surface andthe substantially vertical surface of the respective word line capsprojects toward a longitudinal axis extending centrally through thedigit line contact.

The digit line contact 150 may comprise an upper portion 151laterally-neighboring and extending between the first insulatingmaterial 116 and the semiconductive material 118 and a lower portion 153laterally-neighboring and extending between the word line caps 114. Theupper portion 151 may be horizontally elongated and the lower portion153 may be vertically elongated such that the upper portion 151 and thelower portion 153 are collectively substantially T-shape. As usedherein, the term “horizontally elongated” refers to features (e.g.,structures, devices) having a greater horizontal dimension (e.g., in they-direction of FIG. 9) than a vertical dimension (e.g., in thez-direction of FIG. 9). As used herein, the term “vertically elongated”refers to features having a greater vertical dimension than a horizontaldimension. Put differently, the digit line contact 150 tapers (e.g.,decreases) in width (e.g., a horizontal dimension) as the digit linecontact 150 extends axially (e.g., in the z-direction, along thelongitudinal axis 144) through the semiconductive material 118, thefirst insulating material 116, and the word line caps 114 between thebarrier material 156 and the active region 104.

As previously discussed herein, the transition surface 121 projects(e.g., points, extends) toward the longitudinal axis 144 that extendscentrally through the digit line contact 150. As the peripheral surfaceof the digit line contact 150 is complementary in shape to the opening130, the peripheral surface of the digit line contact 150 is indentedtoward the longitudinal axis 144. The indentation results in thenarrowing, or tapering, of a width of the digit line contact 150relative to the upper portion 151 between the opposing substantiallyvertical surfaces 115 of the word line caps 114 to form the lowerportion 153 of the T-shape.

A comparison of the shape of the digit line contact opening 30 of thetransistor 10 of the conventional DRAM cell and the opening 130 of thesemiconductor device 100 is provided by FIGS. 11 and 12, respectively.As illustrated in FIG. 11, material of the word line caps 20 is at leastpartially removed during formation of the transistor 10 of theconventional DRAM cell. Accordingly, with reference to FIGS. 1 and 11,the word line caps 20 are etched such that the sloped surface 13 extendsto and intersects with the substantially horizontal surface 15 at thetransition surface 17 (e.g., corner) that projects toward (e.g., into)the word line cap 20 and away from the longitudinal axis 31.Accordingly, the digit line contact opening 30 in which the digit linecontact 22 (FIG. 1) is formed is substantially U-shaped. Removal of aportion of the word line caps 20 results in an increased surface area ofthe digit line contact 22, which increases coupling capacitance betweenthe neighboring digit lines. In contrast and as illustrated in FIGS. 9and 12 and as previously described herein, the word line caps 114according to embodiments of the disclosure are substantially unetched,resulting in a decreased surface area of the digit line contacts 150,which decreases coupling capacitance between neighboring digit lines.Semiconductor devices (e.g., the semiconductor device 100) of FIGS. 9and 10 in accordance with embodiments of the disclosure may be used inembodiments of electronic systems of the disclosure. For example, FIG.13 is a block diagram of an illustrative electronic system 200 accordingto embodiments of disclosure. The electronic system 200 may comprise,for example, a computer or computer hardware component, a server orother networking hardware component, a cellular telephone, a digitalcamera, a personal digital assistant (PDA), portable media (e.g., music)player, a Wi-Fi or cellular-enabled tablet such as, for example, aniPad® or SURFACE® tablet, an electronic book, a navigation device, etc.The electronic system 200 includes at least one memory device 202. Theat least one memory device 202 may include, for example, memory cellsarranged in an array of rows and columns, the memory cells comprising anembodiment of the semiconductor devices 100 previously described withreference to FIGS. 2-10. The electronic system 200 may further includeat least one electronic signal processor device 204 (often referred toas a “microprocessor”). The electronic system 200 may further includeone or more input devices 206 for inputting information into theelectronic system 200 by a user, such as, for example, a mouse or otherpointing device, a keyboard, a touchpad, a button, or a control panel.The electronic system 200 may further include one or more output devices208 for outputting information (e.g., visual or audio output) to a usersuch as, for example, a monitor, a display, a printer, an audio outputjack, a speaker, etc. In some embodiments, the input device 206 and theoutput device 208 may comprise a single touchscreen device that can beused both to input information to the electronic system 200 and tooutput visual information to a user. The one or more input devices 206and output devices 208 may communicate electrically with at least one ofthe memory device 202 and the electronic signal processor device 204.

Accordingly, in embodiments of the disclosure, an electronic systemcomprises an input device, an output device, a processor device operablycoupled to the input device and the output device, and a memory deviceoperably coupled to the processor device. The memory device comprises adigit line contact having a perimeter defined by laterally-neighboringword line caps, an insulating material, and a semiconductive material. Asubstantially horizontal surface, a substantially vertical surface, anda transition surface therebetween of the respective word line capsdefine a portion of the perimeter of the digit line contact. Thetransition surface of the word line caps projects toward a longitudinalaxis extending centrally through the digit line contact.

While certain illustrative embodiments have been described in connectionwith the figures, those of ordinary skill in the art will recognize andappreciate that embodiments encompassed by the disclosure are notlimited to those embodiments explicitly shown and described herein.Rather, many additions, deletions, and modifications to the embodimentsdescribed herein may be made without departing from the scope ofembodiments encompassed by the disclosure, such as those hereinafterclaimed, including legal equivalents. In addition, features from onedisclosed embodiment may be combined with features of another disclosedembodiment while still being encompassed within the scope of thedisclosure.

1. A method of forming a semiconductor device, the method comprising:forming a semiconductive material extending betweenlaterally-neighboring word lines, the laterally-neighboring word lineshaving respective word line caps thereon, thereon; forming an insulatingmaterial adjacent the word line caps; forming another semiconductivematerial adjacent the insulating material; selectively removing aportion of each of the another semiconductive material, the insulatingmaterial, and the semiconductive material without substantially removinga material of the word line caps to form an opening through the anothersemiconductive material, through the insulating material, and laterallybetween the word line caps; and forming a conductive material in theopening.
 2. The method of claim 1, wherein selectively removing aportion of each of the another semiconductive material, the insulatingmaterial, and the semiconductive material comprises exposing opposingsubstantially vertical surfaces of the another semiconductive material,opposing substantially vertical surfaces of the insulating material,substantially horizontal surfaces of the word line caps, opposingsubstantially vertical surfaces of the word line caps, and asubstantially horizontal surface of the semiconductive material.
 3. Themethod of claim 2, wherein forming a conductive material in the openingcomprises filling the opening with the conductive material such that theconductive material is formed adjacent the opposing substantiallyvertical surfaces of the another semiconductive material, the opposingsubstantially vertical surfaces of the insulating material, thesubstantially horizontal surfaces of the word line caps, the opposingsubstantially vertical surfaces of the word line caps, and thesubstantially horizontal surface of the semiconductive material.
 4. Themethod of claim 2, wherein forming a conductive material within theopening comprises forming a digit line contact to have a shapecomplementary to a shape of the opening defined by the opposingsubstantially vertical surfaces of the another semiconductive material,the opposing substantially vertical surfaces of the insulating material,the substantially horizontal surfaces of the word line caps, and theopposing substantially vertical surfaces of the word line caps.
 5. Themethod of claim 4, further comprising forming a digit line over thedigit line contact and over the another semiconductive material.
 6. Themethod of claim 1, wherein selectively removing a portion of each of theanother semiconductive material, the insulating material, and thesemiconductive material further comprises exposing a transition surfaceof the word line caps, the transition surface extending between asubstantially horizontal surface of each of the word line caps and asubstantially vertical surface of each of the word line caps, thetransition surface projecting toward a longitudinal axis of the opening,the longitudinal axis extending centrally through the opening.
 7. Themethod of claim 1, wherein selectively removing a portion of each of theanother semiconductive material, the insulating material, and thesemiconductive material comprises etching the another semiconductivematerial, the insulating material, and the semiconductive material.
 8. Amethod of forming a semiconductor device, the method comprising: forminga semiconductive material extending laterally between neighboring wordlines,. the neighboring word lines having respective word line capsthereon; forming a first material adjacent the word line caps; forming asecond material adjacent the first material; forming an opening throughthe second material, through the first material, and at least partiallyinto the semiconductive material between the respective word line caps,the opening defined by: opposing substantially vertical surfaces of thesecond material, opposing substantially vertical surfaces of the firstmaterial, substantially horizontal surfaces of the word line caps,opposing substantially vertical surfaces of the word line caps, andtransition surfaces, each of the transition surfaces extending betweenone of the substantially horizontal surfaces of the word line caps andone of the substantially vertical surfaces of the respective word linecaps, the transition surfaces projecting toward a longitudinal axisextending centrally through the opening; and forming a conductivematerial in the opening.
 9. The method of claim 8, wherein forming anopening through the second material, through the first material, and atleast partially through the semiconductive material between therespective word line caps comprises selectively etching the secondmaterial, the first material, the semiconductive material, and the wordline caps.
 10. The method of claim 9, wherein selectively etching thesecond material, the first material, the semiconductive material, andthe word line caps comprises exposing the second material, the firstmaterial, the semiconductive material, and the word line cap material toa boron trichloride plasma gas.
 11. The method of claim 9, whereinselectively etching the second material, the first material, thesemiconductive material, and the word line caps comprises etching thesecond material, the first material, and the semiconductive material ata first etch rate and etching the word line caps at a second etch rate,the first etch rate being greater than the second etch rate.
 12. Themethod of claim 11, wherein etching the second material, the firstmaterial, and the semiconductive material the first etch rate andetching the word line caps at the second etch rate comprises selectingthe first etch rate to be between about five times and about ten timesgreater than the second etch rate.
 13. The method of claim 8, furthercomprising forming a digit line adjacent the second material and theconductive material.
 14. The method of claim 8, wherein: forming thefirst material comprises forming an insulating material; material andforming the second material comprises forming another semiconductivematerial.
 15. An electronic device, comprising: a digit line contactcomprising a lower portion vertically protruding from an upper portion,the upper portion having a greater width than the lower portion, thelower portion having substantially vertical sidewalls; word line capsdirectly laterally adjacent the lower portion of the digit line contact;and word lines adjacent the word line caps.
 16. The electronic device ofclaim 15, wherein the word line caps comprise: a substantiallyhorizontal upper surface; and substantially vertical sidewalls adjacentthe substantially vertical sidewalls of the digit line contact.
 17. Theelectronic device of claim 15, wherein the upper portion of the digitline contact directly vertically overlaps at least a portion of the wordline caps.
 18. An electronic device, comprising: word lines; word linecaps adjacent the word lines; an active region between the word lines;and a digit line contact adjacent the active region, the digit linecontact comprising a portion directly adjacent substantially-verticalsidewalls of the word line caps.
 19. The electronic device of claim 18,wherein the digit line contact further comprises another portiondirectly adjacent a substantially horizontal upper surface of the wordline caps.
 20. The electronic device of claim 18, wherein the digit linecontact defines a substantially T-shaped cross-section.